Polyamphiphiles

Sallenave X, Bazuin CG. Interplay of ionic, hydrogen-bonding, and polar interactions in liquid crystalline complexes of a pyridylpyridinium polyamphiphile with (azo)phenol-functionalized molecules. Macromolecules 2007 40 5326-5336. 

Vuillaume PY, Bazuin CG. Self-assembly of a tail-end pyridinium polyamphiphile complexed with n-aUcyl sulfonates of variable chain length. Macromolecules 2003 36 6378-6388. 

A large number of macromolecules possess a pronounced amphiphilicity in every repeat unit. Typical examples are synthetic polymers like poly(l-vinylimidazole), poly(JV-isopropylacrylamide), poly(2-ethyl acrylic acid), poly(styrene sulfonate), poly(4-vinylpyridine), methylcellulose, etc. Some of them are shown in Fig. 23. In each repeat unit of such polymers there are hydrophilic (polar) and hydrophobic (nonpolar) atomic groups, which have different affinity to water or other polar solvents. Also, many of the important biopolymers (proteins, polysaccharides, phospholipids) are typical amphiphiles. Moreover, among the synthetic polymers, polyamphiphiles are very close to biological macromolecules in nature and behavior. In principle, they may provide useful analogs of proteins and are important for modeling some fundamental properties and sophisticated functions of biopolymers such as protein folding and enzymatic activity. 

Summarizing the findings of this study, we can state the following observations. (1) Polyamphiphiles such as polysoaps display in organic media selective interactions with alkali metal ions (see, for example, in Figure 5, the pH shift from Na to Cs" ). (2) Non-ideality is observed and the amount of free charges is negligible. 

Interest in these alkyl modifled polymeric structures was relatively low for some time, but about 20 years ago was heightened when it was realized that interalkyl chain association, as well as intrachain association, could take place, effectively increasing the molecular weight of the polymer and, therefore, the viscosity of the solution. Hence the term associative thickener evolved and now includes polyamphiphilic structures, i.e., not necessarily only polyionic structures. The presence of hydrophobic groups endows these polymers with surface and interfacial activity and hence with potential as foam, emulsion, and suspension stabilizers as well as surface conditioners. 

As surfactants will compete for hydrophobic sites in an aqueous solution (or interface), it can be expected that many properties of hydrophobically modified polymers will change, depending on the exact conditions of the solution. These can include increases, or decreases, in viscosity and such properties as foaming, emulsification, and wetting. For example, Danino et al. (94) report a rather complete study, using several techniques, of the polyamphiphile poly(disodium maleate-coalkylvinylether) and its mixtures with anionic or nonionic surfactants that have a disruptive effect on the association of this polymer. 

Fig. 10. Schematic picture of organized organization of polyamphiphile (e.g., PSt/PEO) molecules.

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